The current art for disk laser pumping involves either complex arrays of mirrors to redirect pump light from a conventional array into the disk many times to achieve both efficient absorption and uniformity or an array of diodes placed around the rim of the disk pumping through the rim towards the center. Both suffer from complexity and the former is not as rugged as applications demand. Also, both suffer from scalability limitations for higher power.
The current art is represented by the laser technology such as Giesen's multi-pass face pumped thin disk laser (see C. Stewen, K. Contag, M. Larionov, A. Giesen, and H. Hugel, “A 1-kW CW thin disc laser”, IEEE Journal of Selected Topics in Quantum Electronics, 2000, 6(4): 650-657). Patents related to the work of Giesen and others include, U.S. Pat. No. 6,438,152 to Contag et al. disclosing a complex system with a plurality of pumping branches and U.S. Pat. No. 6,577,666 B2 to Erhard et al. with a plurality of optical refocusing legs. Vetrovec's proposal of edge pumping a disk gain medium (see J. Vetrovec, “Compact active mirror laser (CAMIL)”, SPIE, Photonics West Laser '2002 Conference, San Jose, Calif., Jan. 22–26, 2001) also requires complex systems with many optical components and also have pump power delivery and laser outputs which are most often highly non-uniform. U.S. Pat. Nos. 6,603,793 B2 and 6,625,193 B2 to Vetrovec provide several arrangements of gain elements, diode arrays, optical medium and optical coatings to achieve high power lasers; however, all arrangements are unlike the arrangement of elements in the present invention.
In addition to the above, annular or circular arrangements of laser diode bars mounted in a dielectric block are disclosed in U.S. Pat. No. 5,627,850 to Irwin et al. and U.S. Pat. No. 6,647,037 B2 to Irwin. U.S. Pat. No. 6,661,827 B2 to Lam et al. discloses a radial array of laser diodes mounted in a segmented conductive ring surrounding a laser rod.
None of the prior art arrangements of diode bars, gain elements, or optical elements have the configuration of an open ring as disclosed herein. Not only does the present invention have a unique configuration, the invention meets the commercial need for a laser pump that is scalable to high power laser output, uses fewer optical elements, and is easy to adjust the pump power delivery and laser output to provide improved uniformity.